Multiple functionalities are prevalent in personal portable and/or mobile wireless communications instruments (collectively in this document, “mobile terminals”). It is now common for a mobile terminal to include a satellite positioning system (SPS) such as a global positioning system (GPS). A GPS includes at least one receiver capable of receiving signals from satellites. A GPS receiver also includes radio frequency circuitry to receive position signals from a plurality of satellites. A GPS receiver also includes a power supply system. The power supply system includes at least one battery and an alternative external power connector for connecting a mobile terminal to an external power source. A GPS receiver also may include at least one microprocessor. The microprocessor includes at least one storage medium such as read-only memory (ROM). The microprocessor is operatively connectable to the circuitry and power supply system of the mobile terminal.
A GPS receiver is an electronics unit that receives and conditions a radio frequency (RF) input signal. A receiver may perform various types of signal conditioning such as low noise amplification, filtering, and related functions. Designing a receiver is challenging due to performance requirements, power consumption, and similar considerations. High performance is required to meet differing system specifications and/or to achieve performance criteria that change to meet different demands. Performance of a receiver may be characterized by various parameters. The parameters include at least linearity, dynamic range, and noise performance.
Linearity refers to the capability of a receiver to amplify a signal without generating a significant distortion. As disclosed in this document, linearity may be adjusted to improve battery life. Adjustment of linearity in a receiver used in a mobile terminal such as a cellular phone having GPS capability may extend battery life between recharges, which is highly desirable.
Unlike conventional digital receivers, an SPS receiver may be required to perform a variety of tasks requiring comparatively significant power use. Such tasks may include, for example, maintaining tables, monitoring satellite signals, and calculating varying positions of the mobile terminal and satellites. Preservation of battery life in a mobile terminal therefore is desirable.
Although a mobile terminal may be operatively connected to an external power source, preservation of battery life in a mobile terminal is desirable for a number of reasons. One reason is in anticipation of use of the internal battery of the mobile terminal when the mobile terminal is disconnected from an external power source. Another circumstance arises from a demand to maximize navigation performance whether the mobile terminal is connected to an external power source or is relying on the internal battery of the mobile terminal. Another circumstance arises from emergency use. Examples of emergency use include the need to maximize both navigation performance and communication performance during an urgent situation involving, for example, 911 transmissions, an avalanche alert, and similar emergencies. In such cases the emergency will take precedence over considerations of battery life. However, the more that battery life is preserved during use, the better the chances of coping with such emergencies, especially under circumstances in which recharging may not be an immediate option.
At least one solution proposed for extending battery life of a mobile terminal is to automatically switch a navigation receiver to low linearity if the transmitter power drops below a preset or preprogrammed value or threshold. A limitation of that approach is that it does not factor into consideration the multiplicity of functionalities, tasks and unanticipated demands that may arise in connection with the use of a mobile terminal equipped with GPS capabilities.
A need exists in the industry, therefore, for a new, useful and improved method of improving and extending battery life that is capable of using a number of operational factors and parameters to adjust receiver linearity so as to improve and extend battery life.